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bpf: avoid misuse of psock when TCP_ULP_BPF collides with another ULP

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Currently we check sk_user_data is non NULL to determine if the sk
exists in a map. However, this is not sufficient to ensure the psock
or the ULP ops are not in use by another user, such as kcm or TLS. To
avoid this when adding a sock to a map also verify it is of the
correct ULP type. Additionally, when releasing a psock verify that
it is the TCP_ULP_BPF type before releasing the ULP. The error case
where we abort an update due to ULP collision can cause this error
path.

For example,

  __sock_map_ctx_update_elem()
     [...]
     err = tcp_set_ulp_id(sock, TCP_ULP_BPF) <- collides with TLS
     if (err)                                <- so err out here
        goto out_free
     [...]
  out_free:
     smap_release_sock() <- calling tcp_cleanup_ulp releases the
                            TLS ULP incorrectly.

Fixes: 2f857d0460 ("bpf: sockmap, remove STRPARSER map_flags and add multi-map support")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
John Fastabend 2018-08-30 21:25:02 -07:00 committed by Daniel Borkmann
parent 97911e0ccb
commit 597222f72a
1 changed files with 11 additions and 1 deletions
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12
kernel/bpf/sockmap.c
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@ -1462,10 +1462,16 @@ static void smap_destroy_psock(struct rcu_head *rcu)
schedule_work(&psock->gc_work);
}
static bool psock_is_smap_sk(struct sock *sk)
{
return inet_csk(sk)->icsk_ulp_ops == &bpf_tcp_ulp_ops;
}
static void smap_release_sock(struct smap_psock *psock, struct sock *sock)
{
if (refcount_dec_and_test(&psock->refcnt)) {
tcp_cleanup_ulp(sock);
if (psock_is_smap_sk(sock))
tcp_cleanup_ulp(sock);
write_lock_bh(&sock->sk_callback_lock);
smap_stop_sock(psock, sock);
write_unlock_bh(&sock->sk_callback_lock);
@ -1892,6 +1898,10 @@ static int __sock_map_ctx_update_elem(struct bpf_map *map,
* doesn't update user data.
*/
if (psock) {
if (!psock_is_smap_sk(sock)) {
err = -EBUSY;
goto out_progs;
}
if (READ_ONCE(psock->bpf_parse) && parse) {
err = -EBUSY;
goto out_progs;